Arrangement for eliminating squeaking in vehicle brakes

ABSTRACT

In an arrangement for eliminating squeaking in disc-type vehicle brakes, the arrangement comprising an equalizing element arranged between the brake shoe and the brake piston, the improvement that the equalizing element is guided with a certain clearance in a plane parallel to the brake shoe and the surfaces of the element bearing against the brake piston and the brake shoe, respectively, are of considerably different size.

0 United States Patent [1 1 [111 3,876,042 Borjesson Apr. 8, 1975 1ARRANGEMENT FOR ELIMINATING [56] References Cited SQUEAKING lN VEHICLEBRAKES UNITED STATES PATENTS [75] Inventor; Sven Borjesson, Goteborg.Sweden 3.186.518 6/1965 Rodway 188/72.4

[73] Assignee: Aktiebolaget Volvo. Goteborg. FOREIGN PATENTS ORAPPLICATIONS Sweden 1.390.274 1/1965 France 188/722 22 '1 d: Fle Jan 18I974 Przmury E.\'ammerGeorge E. A. Halvosa [21] Appl. No.: 434.594Anornev. Agent, or FirmYoung & Thompson Related US. Application Data[63] Continuation of Ser. No. 185.779. Oct. 1. 1971. [57] TR T abandonedin an arrangement for eliminating squeakmg m disctype vehicle brakes.the arrangement comprising an [30] Foreign Appncafion priority Dataequalizing element arranged between the brake shoe Oct 6 [970 Sweden3570/70 and the brake piston. the improvement that the equalizingelement is guided with a certain clearance in a plane parallel to thebrake shoe and the surfaces of l88/73i?5l,61d82/52/(l)(7) the clementbearing against the brake pismn and the [58] Field 72 4 5 brake shoe.respectively. are of considerably different SEC.

5 Claims, 2 Drawing Figures *4 is exposed to splashingiwater and othercontaminants,

the joint between the piston'4 and the cylinder wall is protected by anelastic muff 6. Arranged on either side of the brake disc 1 so as to bemovable towards and This is a continuation, of .application Ser. No;

185,779, filed Oct. 1, 197l, now abandoned.

The invention relates to an'arrangement for preventing squeaking indisc-type vehicle brakes and includes an equalizing element disposedbetween the brake shoe and the brake shoe engaging surface. In drumbrakes and also in disc brakes, mechanical vibrations of high frequency,e.g. of the order of 3000-4000 Hz, are generated when the brakes areapplied, owing to the friction forces occurring between the brake liningand the brake drum or brake disc, respectively. These vibrations causeunpleasant sound effects, which have been found very difficult toovercome.

Various attempts have been made to eliminate or dampen these vibrations,for example by increasing the stiffness of the brake shoe and/or thebrake disc or to increase the thickness thereof, but these measures haveonly resulted in changing the frequency of the vibrations. One method ofreducing squeaking in brake drums is to mount on the drum secondary,arcuate resonance elements, the ends of which are caused to abut thedrum and the centre portion of which are secured tightly adjacent thedrum, while the intermediate portion is curved outwardly, whereupon asthe drum vibrates the ends of the elements move relative to the drum andtake up the energy of vibration.

It has been discovered, however, that the vibrations of a disc brake canbe reduced and squeaking completely eliminated when the vibrationmovements of the brake shoe can be dampened by friction against a movingelement which comprises an intermediate link between the brake pistonand the brake shoe. The surfaces of the element which bear'against thebrake shoe and the brake piston shall be of different size, wherebyuniform distribution of the surface pressure between the brake shoe andthe brake piston is obtained independently of whether the brake discand/or the brake shoe are positioned obliquely in relation to the brakepiston.

The present invention is mainly characterized in that the equalizingelement is guided with a certain clearance in a plane which extendsparallel to the brake shoe, and in that the size of the surface of theelement which bears against the brake shoe differs considerably from thesurface of the element which bears against the brake piston.

The invention will now be described with reference to the accompanyingdrawing, in which FIG. 1 illustrates diagrammatically a sectional sideview of a disc brake along the line II in FIG. 2, and

FIG. 2 is a partially sectioned plan view of the disc brake.

The disc brake is of the type normally found in vehicles and comprises abrake disc 1 capable of rotating with a wheel axle, and a yoke 2 securedto a stationary portion of the vehicle. The yoke surrounds the edgeportion of the brake disc 1 and on either side of the disc and at rightangles thereto are mounted brake cylinders 3 which are connected to acommon hydraulic brake system. Each brake cylinder 3 is provided with apiston 4, which is movable at right angles to the brake disc and whichis accurately guided in the brake cylinder and sealed against its innerwall by means of a seal ring 5. Since the outwardly projecting end ofthe brake piston away from said disc is a brake shoe 7 provided with abrake lining 8 which faces the disc 1. The brake shoes 7 are jounalledon pins 9 which are mounted in the yoke 2 and guided for restrictedmovement thereby. For the purpose of restricting the movement of thepins 9, the brake shoes 7 are provided with a radial flange 10 in whichare disposed through-holes 11 for the pins 9. the arrangement being suchthat the brake shoes 7 are able to move freely without the risk ofjamming.

When the brakes are applied, forces occur which attempt to force thebrake shoes 7 to accompany the rotary movement of the disc. Owing to thefree but limited movement of the brake shoes 7, these forces tend toincline the brake shoes 7 so that they do not lie fully perpendicular tothe axis of the brake piston 4. The brake application force is thus notdistributed symmetrically over the brake lining 8. The frictionoccurring between the disc 1 and the brake lining 8 gives rise tovibrations in the brake shoes 7, which in turn can result in a squeakingsound.

In accordance with the invention, a suitably circular equalizing element12 is inserted in a recess 13 disposed in the end of the brake piston 4,the recess 13 having substantially the same shape as the rear side ofthe element 12, but is sufficiently large to permit slight movement ofthe element 12 in a plane which extends parallel to the brake. The sidewalls of the recess 13 together with a central outwardly projecting peg14 which fits into a corresponding recess 15 in the element 12, preventsthe element from moving out of the recess 13 in the piston 4. The side16 of the equalizing element 12 facing the brake shoe 7 is convex or hassome other suitable configuration, e.g. frusto-conical, so that only anextremely small portion of the side 16 bears against the brake shoe 7,whereby the equalizing element 12 operates as a type of ball joint sothat the brake force over the brake shoe 7 and the brake lining 8 alwaysuniformly distributes the surface pressure irrespective of whether thebrake shoe 7 is obliquely positionedrelative the brake disc 1 or not.Thus, owing to its restricted movement the equalizing element 12 willoperate as any energy absorbing element which dampens any vibratorymovement of the brake shoe 7 and thus prevents squeaking when the brakesare applied. It should be mentioned that although the actual area ofcontact between the side 16 of the element and the brake shoe 7 is verysmall, it should preferably not be in the form of a spot contact.

Although the invention has been described and illustrated with referenceto one embodiment thereof, the invention can be modified within thescope of the following claims. For example, the equalizing element 12may be let into a recess in the brake shoe 7 with the small supportsurface arranged so as to face the brake piston 4.

What 1 claim is:

1. A disc-type vehicle brake, comprising a brake shoe having a brakelining, a brake piston actuating the brake shoe, and an equalizingelement disposed between and bearing on two sides of the brake shoe andbrake piston that face each other, one of said shoe and piston having arecess therein in which said element is disposed with clearance in adirection parallel to said shoe, said element having a substantiallyconvex surface that bears against the other of said shoe and piston,said element and the bottom of said recess having flat surfaces whichare in sliding contact with each other over an area which is parallel tosaid shoe and which is substantially greater than the area of contactbetween said element and the other of said shoe and piston.

2. A brake as claimed in claim 1, said substantially convex surfacebeing frusto-conlcal.

3. A brake as claimed in claim 1, said recess being in said piston, saidpiston having a frusto-conical peg at

1. A disc-type vehicle brake, comprising a brake shoe having a brakelining, a brake piston actuating the brake shoe, and an equalizingelement disposed between and bearing on two sides of the brake shoe andbrake piston that face each other, one of said shoe and piston having arecess therein in which said element is disposed with clearance in adirection parallel to said shoe, said element having a substantiallyconvex surface that bears against the other of said shoe and piston,said element and the bottom of said recess having flat surfaces whichare in sliding contact with each other over an area which is parallel tosaid shoe and which is substantially greater than the area of contactbetween said element and the other of said shoe and piston.
 2. A brakeas claimed in claim 1, said substantially convex surface beingfrusto-conical.
 3. A brake as claimed in claim 1, said recess being insaid piston, said piston having a frusto-conical peg at the center ofthe bottom of said recess that fits into a complementary recess in theflat surface of said element.
 4. A brake as claimed in claim 3, saidrecess in said piston having a frusto-conical outer side wallcomplementary to the shape of the outer side wall of said element.
 5. Abrake as claimed in claim 1, said element being circular and having adiameter several times its thickness.